Description:

Protecting a pipeline from corrosion is not only a task for the manufacturer or builder, but also for the network designer and the end user. The phenomenon of corrosion may be due to an insufficiently balanced composition of the liquid flowing through the pipes, an incorrect combination various metals or, finally, insufficient attention to pipeline protection.

HOW TO PROTECT A PIPELINE FROM CORROSION

Protecting a pipeline from corrosion is not only a task for the manufacturer or builder, but also for the network designer and the end user. The phenomenon of corrosion may be due to an insufficiently balanced composition of the liquid flowing through the pipes, an incorrect combination of various metals, or, finally, insufficient attention to protecting the pipeline.

Pipeline corrosion is a phenomenon caused mainly by electrochemical reactions of metal oxidation when interacting with moisture. The metal gradually changes at the ionic level and, disintegrating, disappears from the surface of the pipe. Oxidation characterizing the phenomenon of corrosion metal pipelines, can occur for various reasons and, therefore, arises based on different mechanisms. The oxidation process may depend on the nature of the fluid flowing through the pipeline or on the properties of the environment in which the pipeline is installed. In this regard, when choosing the most appropriate methods of counteracting corrosion mechanisms, it is necessary to take into account the characteristics of the situation in which it is observed. In some cases, corrosion control is carried out by taking enhanced measures to chemically treat the leaking liquid in order to correct its corrosive properties, in other cases by using protective coatings for pipelines (internal or external) or using special methods of so-called “cathodic protection”. First of all, careful selection of material for the pipeline is necessary. It seems advisable to use materials that are less susceptible to corrosion (for example, copper or stainless steel).

When used at the initial stage of corrosion, a continuous thin surface oxide film (“inert film”) is formed, which then protects the underlying metal from the effects of corrosion. However, even on such materials, for various reasons, pockets of corrosion can form. The reason is uneven film formation or its breakthrough. The use of more valuable materials is not always justified due to their high cost.

Chemical treatment of aggressive water

Water flowing through the pipeline may have aggressive properties. This is often due to the treatment of such water with chlorine or the processes of coagulation and flocculation that occur in the water directly at the water treatment plant. Aggressiveness may be due to the content of oxygen, chlorine, carbonates and bicarbonates in water. Aggressiveness decreases with increasing levels of acidity and hardness and increases with increasing temperature and the content of dissolved air and carbon dioxide.

The main goal of chemical water treatment is to convert potentially aggressive water into slightly calcifying water. Moderate hardness is, in fact, desirable, since it promotes the formation of calcium salt deposits on the inner surface of the pipe, which protect the metal. By adding appropriate inhibitory substances to water, you can slow down the corrosion process, reducing it to less dangerous manifestations (uniform corrosion instead of deep local), and also promote - through a chemical reaction - the formation of lime deposits, which, tightly adhering to the metal, form a coating that protects it from corrosive effects. In public water supply networks, water treatment is reduced mainly to the addition of calcium, or soda (NaOH), or sodium carbonate (Na 2 CO 3). In sections of the water supply system that ensure the distribution of water to individual water collection points, treating water with special “sequestering” additives (mainly polyphosphates) is considered an effective method of anti-corrosion protection. The main purpose of additives of this kind is to correct excessive water hardness, which could otherwise lead to the formation of unwanted pockets of lime deposits. In galvanized steel pipelines, when polyphosphates, phosphates or silicates are added to water, a film of polyphosphate, phosphate or zinc or iron silicate is formed on the inner surface of the pipeline, protecting the metal from corrosion. The use of such reagents in water supply networks for drinking purposes is permitted subject to compliance with the requirements established by the current sanitary and epidemiological regulations.

Protective coatings

Coatings can be applied to both internal and external external surfaces pipeline. The protective coating forms the protection of the pipeline, which can be of the active or passive type. In some cases, both types of protection may be combined. In the case of active protection, the coating creates conditions that prevent the spread of metal corrosion. Surface steel pipes is covered with a more or less dense layer of an electrochemically less noble metal (usually zinc), which, while protecting the base metal, takes on the effects of corrosion. Active protection provides greater protection inner surface pipes from the corrosive effects of leaking liquid. WITH outside such protection forms a base coating enhanced by passive protection.

The task of passive protection is to protect metal pipes from destructive effects environment. In buried areas of water pipelines, it is very important to reliably protect the metal from direct contact with the ground. Similar protection is used to achieve - with the help of an internal coating - in pipelines intended for the delivery of particularly aggressive types of water. The application of protective layers made of varnishes, paints or enamels creates a continuous impenetrable barrier that protects the underlying metal from the corrosive effects of the environment.

For this purpose, bituminous products are most often used, obtained from the distillation of coal or oil or from synthetic resins, thermoplastic (polyethylene, polypropylene, polyamides) and thermosetting (epoxy, polyurethane, polyesters).

Before coating, it is necessary to properly prepare the surface of the pipe to be treated and thoroughly clean it of anything that may be harmful in terms of corrosion (moisture, varnish residues, grease or oil stains, dirt or dust, rust). For external protection of open pipelines, you can resort to paint coatings or powder plastic materials. Coating is applied in various ways depending on the pipeline material. Liquid formulations are applied with a brush, by immersion in a solution or by spraying from a pistol.

Powdered substances (mostly plastic materials) are applied to a pipe preheated to a temperature exceeding the melting point of the powder. The powder is applied to the surface of the pipe electrostatically or by air spraying. Thermoplastic materials can also be applied by extrusion. Surface layers of metal (such as zinc) are applied by immersing a pipe in molten metal or by electrolytic deposition. Another method often used to cover buried pipelines is to uniformly apply a continuous film of a protective material having good adhesion properties to the previously cleaned pipe, followed by a protective layer of a bitumen mixture and two layers of glass wool (or fabric) impregnated with bitumen mixture to provide resistance to external influences.

It's better if protective treatment cut pipes will be carried out at the manufacturer's factory.

When laying the protective coating on site, only the seams and couplings, as well as possible areas of damage to the factory coating, are sealed.

Pipes that have a factory coating should be protected during stacking, transportation and installation work from impacts, scratches and other mechanical impacts that can damage the bitumen layer. It should be taken into account that protective treatment loses its original properties after a certain time. Hence the need for periodic network inspection, routine and preventative maintenance.

A buried pipeline is susceptible to corrosion due to the aggressiveness of the soil. Depending on the properties of the soil (more precisely, its resistance parameters) and the metal from which the pipeline is made, corrosive batteries are formed. The metal, which acts as an anode relative to the soil, which in this case acts as a cathode, tends to decompose and go into solution.

One type of protective measures is passive protection. For laying the pipeline, pipes with a protective moisture-proof coating with insulating couplings. In this case, the electrical length of the pipeline is disrupted, and the exchange of electric current between the pipes and the soil is inhibited. It should be recognized that this approach does not always give a 100% result, since in places where the protective coating of pipes is damaged during the process pipeline laying, the formation of corrosion spots is possible. Corrosion can be combated using the “cathodic protection” method: if the potential of the metal is artificially lowered, the anodic reaction is suppressed. To do this it is necessary to implement electrical connection pipeline to a network containing an anode. The so-called “sacrificial anode” is made of a metal that has a higher electronegativity, that is, less noble than iron. As a rule, magnesium alloy is used for these purposes. With this connection, corrosion is localized on magnesium, which slowly decomposes itself and protects the pipeline. When practical application This technology should first of all measure the degree of soil aggressiveness.

Then, in areas where it is necessary to protect the pipeline, a certain number of consumable anodes are dug in at design points. The weight and number of anodes are determined in such a way as to ensure anti-corrosion protection of the pipeline for a period of 10–15 years.

Another method that protects metal from soil aggressiveness is “induced current” protection. For this, an external direct current source is used, which comes from a power supply device consisting of a transformer and a rectifier. The positive pole of the power supply is connected to the anode dissipator (grounding, consisting of a graphite or iron-containing anode), the negative pole is connected to the pipeline representing the protected object. The transmitted protective current is determined by the parameters of the pipeline (length, diameter, degree of insulation available) and the degree of soil aggressiveness. The current dissipated by grounding creates an electric field that envelops the pipe and lowers its potential, which gives a protective effect. Reliability and efficiency cathodic protection are ensured, among other things, by periodic inspection of the network, checking the functionality of the equipment used and timely troubleshooting.

Stray current

Stray current is an electric current that appears in some soils from the dispersion of electrified, for example, railway (tram) tracks, where the rails act as return conductors of supply substations. Another source of stray current can be the grounding of electrical industrial equipment. As a rule, this is a high current, and it affects primarily the pipeline, which has good conductivity (in particular, with welded joints). Such a current enters the pipe at a certain point, which acts as a cathode, and, having overcome a more or less long section of the pipeline, exits at another point, which acts as an anode. The electrolysis that occurs during this process causes corrosion of the metal. The passage of current in the area from the cathode to the anode causes the transition of iron-containing particles into solution and over time can lead to thinning and ultimately perforation of the pipe. The higher the strength of the passing current, the more significant the damage. The corrosive effect of stray current is, of course, more destructive than the effect of corrosive batteries formed due to the aggressiveness of the soil.

“Electrical drainage” measures are effective against it. The essence of the technique is as follows: at a certain point, the pipeline is connected directly to a source of stray current (for example, to a substation or railway track) using a special cable with low electrical resistance. The connection must be properly polarized (using unidirectional adapters) so that the current always flows in the direction from the pipeline to the source of dispersion. Electrical drainage requires strict adherence to routine inspections, careful adjustment and regular inspection. Most often, this technique is combined with other methods of protection.

Reprinted with abbreviations from RCI Magazine No. 8. 2003.

Translation from Italian S.N. Bulekova.

Sacrificial anode

The buried magnesium block, due to the position occupied by magnesium on the electrochemical potential scale relative to iron, behaves like an anode in the corrosion battery formed between it and the steel pipeline.

The current generated by the electromotive force of the corrosive battery moves in the direction “anode - soil - pipe - connecting cable - anode”. The slow decomposition of magnesium protects the pipeline from corrosion.

This system is mainly used for protection steel tanks and pipelines of limited length (from several hundred meters to several kilometers).

Typically, the anode is placed in a cotton (or jute) bag in a clay mixture, the purpose of which is to ensure uniform consumption of the anode and the required level of moisture, and also to prevent the formation of a film that impedes its decomposition.

Access to electrical cable and checking the condition of the protective coating by measuring the battery current is provided through a special well.

Cathodic protection "induced current"

To organize such protection, a direct current generator is required, to the negative pole of which the protected pipeline is connected. The positive pole is connected to a system of anode diffusers buried in the same area of ​​soil.

The connecting cable must have low electrical resistance and good insulation. The electric current produced by the generator is transmitted to the soil through anodes and supplied to the pipeline. The pipeline acts as a cathode and is thus protected from corrosion. The current flows along the following route: electric generator - connecting cable - dissipator electrode - soil - protected metal structure - connecting cable - electric generator. The anodes used are of a low-consumption type (usually graphite or iron-containing) and are buried 1.5 m at a distance of 50–100 m from the pipeline. A DC generator (125–500 W) usually consists of a rectifier fed from the mains through a transformer.

Corrosion is one of the main problems of all metal structures. Many experts believe that the appearance of rust is an inevitable process, and their only recommendation is to replace metal pipes with plastic ones. However, given the fragility of plastic, such perturbations cannot be carried out everywhere. In addition, the development of corrosion can be slowed down, significantly reducing its destructive effect.

There are several ways to combat corrosion of profile pipes in Moscow, and the simplest of them is to apply special means, forming a protective film on its surface. This medium can be paint, varnish or enamel. Paint coatings are characterized by low gas permeability and gas permeability, as well as water repellency. Such coatings do not allow the metal to come into contact with moisture, oxygen and other aggressive substances that cause corrosion. Paintwork materials are relatively inexpensive and very easy to apply. To do this, use an ordinary brush. A spray option is also available.

The protective qualities of paints and varnishes are maintained for several years, after which the layer must be renewed. They have several disadvantages:

1. Cannot withstand significant mechanical damage.
2. Not resistant to temperature changes.

As a result, over time, cracks form on the surface of painted pipes, so this type of protection should be carried out regularly.

How to properly prepare a pipe for painting

In order to reliably protect a pipe from corrosion, it is necessary not only to use high-quality protective substances, but also to take care of their correct application. First of all, here it is necessary to achieve high adhesion, that is, the quality of adhesion of the applied composition to the metal. This method anti-corrosion profile pipes in Moscow assumes a uniform application layer, absence of air bubbles and porosity. Therefore, the quality of the coating will directly depend on the preparation of the base.

Do you want to know what is the most effective corrosion protection for steel pipes? During operation, metal pipes are constantly exposed to various unfavorable factors. To solve this problem, comprehensive protection of pipelines against corrosion has been specially developed in accordance with SNiP 2.03.11-85 “Protection building structures from corrosion."

External polymer coating — reliable protection against corrosion of steel pipes

Corrosion control methods

This article invites the reader detailed instructions, which describes in detail the basic principles of anti-corrosion protection for metal products. I will tell you how to protect any metal surface from corrosion.

Classification of harmful factors

According to the mechanism of occurrence and the degree of destructive impact, all harmful factors can be roughly divided into several types.

1. Atmospheric corrosion occurs when iron interacts with water vapor contained in the surrounding air, as well as as a result of direct contact with water during precipitation. During the chemical reaction, iron oxide is formed, or, more simply, ordinary rust, which significantly reduces the strength of metal products, and over time can lead to their complete destruction.

Electrochemical corrosion underground destroys even thick-walled pipes

1. Chemical corrosion occurs as a result of the interaction of iron with various active chemical compounds (acids, alkalis, etc.). At the same time, leaking chemical reactions lead to the formation of other compounds (salts, oxides, etc.), which, like rust, gradually destroy the metal.
2. Electrochemical corrosion occurs in cases where an iron product is in an electrolyte environment (an aqueous solution of salts of varying concentrations) for a long time. In this case, anodic and cathodic areas are formed on the surface of the metal, between which an electric current flows. As a result of electrochemical emission, iron particles are transferred from one area to another, which leads to the destruction of the metal product.
3. Exposure to freezing temperatures in cases where pipes are used to transport water, it leads to freezing. Upon transition to a solid state of aggregation, a crystal lattice is formed in water, as a result of which its volume increases by 9%. Being in a confined space, water begins to put pressure on the walls of the pipe, which ultimately leads to their rupture.

Note!

A significant difference in average annual and average daily temperatures leads to significant fluctuations in the total length of the pipeline, which are caused by the linear thermal expansion of the material. To prevent pipe rupture and damage load-bearing structures, after a certain distance on the line it is necessary to install thermal compensators.

Soil analysis

In order to choose the most effective method protection, it is necessary to have accurate information about the nature of the environment and the specific operating conditions of the steel pipeline. In case of laying internal or overhead line this information can be obtained on the basis of subjective observations, as well as based on the average annual climate regime for a given region.

In the case of laying an underground pipeline, the corrosion resistance and durability of the metal largely depend on the physical parameters and chemical composition soil, so before digging a trench with your own hands, you need to submit soil samples for analysis to a specialized laboratory.

The most important indicators that need to be clarified during the analysis process are the following soil qualities:

1. Chemical composition and the concentration of salts of various metals in groundwater. The density of the electrolyte and the electrical permeability of the soil largely depend on this indicator.
2. Qualitative indicator of acidity soil, which can cause both chemical oxidation and electrochemical corrosion metal
3. Electrical resistance of the earth. The lower the electrical resistance value, the more susceptible the metal is to the destructive effects caused by electrochemical emission.

Note!

To obtain objective analysis results, soil samples must be removed from the soil layers in which the pipeline will pass.

Low temperature protection

In the case of underground or overhead installation of water and sewer networks, the most important condition for their uninterrupted operation is to protect the pipes from freezing and maintain the water temperature at a level not lower than 0°C during the cold season. To reduce the negative impact temperature factor environment, the following technical solutions are used:

1. Laying an underground pipeline at depth, exceeding maximum depth soil freezing for a given region.
2. Thermal insulation air and underground lines with help various materials with low thermal conductivity (mineral wool, foam segments, foam propylene sleeves).

Foil sleeves made of mineral wool for pipe insulation

1. backfilling pipeline trenches bulk material with low thermal conductivity (expanded clay, coal slag).
2. Drainage adjacent layers of soil in order to reduce its thermal conductivity.
3. Pad underground communications in rigid closed boxes made of reinforced concrete, which ensure the availability air gap between the pipe and the ground.

The most progressive method of how to protect pipes from freezing is to use a special casing consisting of a shell made of thermal insulation material, inside of which an electric heating element is placed.

Note!

The depth of soil freezing for each specific region, as well as the methodology for its calculation, is regulated by regulatory documents SNiP 2.02.01-83* “Foundations of buildings and structures” and SNiP 23-01-99* “Building climatology”.

External waterproofing coating

The most common way to combat metal corrosion is to apply a thin layer of durable, waterproof protective material to its surface.

I'll bring simple examples:

1. The most common protective coating option is regular waterproof paint or enamel. For example, the protection of a gas pipe passing through the air is always done with weather-resistant yellow enamel;
2. Underground water and gas pipelines are assembled from steel pipes, which are pre-coated on the outside with a thick layer of bitumen mastic and then wrapped in thick technical paper:
3. Also high efficiency have coatings made of composite or polymer materials;
4. Cast iron elements sewer communications coated with a thick layer inside and outside cement-sand mortar, which after hardening forms a homogeneous monolithic surface. This way you can protect the support.

To choose the right suitable material for external coating, you need to know that anti-corrosion protection of metal must simultaneously have several qualities.

1. Paintwork after drying it should have a continuous, homogeneous surface with high mechanical strength and absolute resistance to water;
2. Protective film waterproofing material, with the specified properties, must be elastic and not collapse under the influence of high or low temperatures;
3. Raw material to apply the coating it must have good fluidity, high covering ability, as well as good adhesion to the metal surface;
4. Anti-corrosion treatment applied to a dry, clean metal surface;
5. Electrical conductivity. Another indicator of a high-quality insulating material is that it must be an absolute dielectric. Thanks to this property, reliable protection of pipelines is provided from stray currents, which enhance the adverse effects of electrochemical corrosion.

Note!

Most effective solutions For waterproofing metal, it is customary to consider compositions based on bitumen resins, two-component polymer compositions, as well as roll polymer materials on a self-adhesive basis.

Active and passive electrochemical protection

Underground utility lines are more susceptible to corrosion than air and internal pipelines, because they are constantly in an electrolyte environment, which is a solution of salts contained in groundwater.

In order to minimize the destructive effects caused by the reaction of iron with a water-salt electrolyte solution, active and passive methods of electrochemical protection are used.

1. Active cathode method consists in the directional movement of electrons in a direct electric current circuit:

• To do this, a pipeline is connected to the negative pole of the DC source, and an anode grounding rod is connected to the positive pole, which is buried in the ground nearby;
• After applying voltage, electrical circuit closes through the soil electrolyte, as a result of which free electrons begin to move from the ground rod to the pipeline;
• Thus, the grounding electrode is gradually destroyed, and the released electrons react with the electrolyte instead of the pipeline.

1. Passive tread protection pipelines is as follows:

• An electrode made of a more electronegative metal, such as zinc or magnesium, is placed near the iron in the ground;
• The steel pipe and the electrode are connected electrically through a controlled load;
• In the electrolyte environment they form a galvanic couple, which during the reaction causes the movement of electrons from the zinc protector to the protected pipeline.

3.Electrical drainage protection is also a passive method, which is performed by connecting the pipeline to the ground loop:

• The connection is made in accordance with the requirements of the PUE;
• This method helps to get rid of the occurrence of stray currents and is used if the pipeline is located near the contact electrical network of ground or rail transport.

Note!

A clear example of passive protective protection is the well-known zinc coating of iron products, or, more simply, galvanization.

Conclusion

Each of the above methods has its own advantages and disadvantages, so they must be used depending on specific conditions. In conclusion, I can only say that regardless of the chosen method, the cost of repairing and replacing the pipeline will cost much more than the cost of the most complex and time-consuming protection.

Of the different types of posts used to build a fence on summer cottages, in most cases pipes are used. Firstly, the material is from a moderate price category, durable, easy to use. Secondly, it combines perfectly with other materials.
Depending on the type of barrier, different types of pipes are selected. Use round, rectangular and square. Round ones are a little cheaper, but square or rectangular ones are stronger and easier to work with.
Painting fence posts will not only give the fence an aesthetic appearance, but will also protect the pipes from corrosion. Regardless of whether the material was used or new, the preparation requirements are the same.
To pre-treat pipes you will need:

• metal brush;
• brushes for power tools;
• grinding wheels;
• sandpaper;
• personal protective equipment.

The treated surface is thoroughly cleaned of rust and dirt. A suitable tool for this purpose is selected. For removing old paint washing may be necessary. The stores offer a wide range of removers for old paint.

Bitumen mastic

Bitumen mastic is widely used in various construction work both protective and waterproofing material. In the case of support pillars, it is necessary to process that part of the pipes that will be buried or cemented. This will help protect the metal from water and salts dissolved in it.
Paint support pillars for collection is possible before installation. At the same time, the drying time increases, since the lower plane is not painted, and it is simply difficult to work with round material. In addition, the finished surface can be damaged quite easily. Therefore, it is better to apply paint after installation.

If it is planned to conduct welding work, then you need to apply the coating after finishing them, carefully cleaning the welding seams!

Bitumen varnish

The prepared pipes are degreased with an available solvent, and varnish is applied to the surface with a brush. The use of varnish does not require additional primer. If the varnish is too thick, it is diluted with white spirit. When purchasing bitumen varnish, you need to pay attention to the drying time. It can range from 1 to 48 hours.
Due to its high adhesive properties, it can be used both as an independent coating and as a primer.

Paint treatment

When choosing paint, the main thing is to decide on the color scheme and buy material from one manufacturer. This will guarantee that the color scheme will not change. In case of special wishes for color, you will have to use different types. When purchasing for mixing, consultation with a specialist is necessary, since not all paints can be mixed. They can curdle like milk, which can ruin the whole process. And since we're talking about about the dacha, then here we are talking about more economical options.
When painting, oil, acrylic, alkyd and other paints are used. It all depends on your wishes: a matte or glossy finish will be the final product.
Oil paints are considered the most economical, but have a number of disadvantages: they take a long time to dry, cannot withstand high temperatures, and do not protect well from corrosion.
Enamels harden faster, hold better and are more resistant to temperatures.

The ideal option would be acrylic paints. They are non-toxic, water soluble, and can withstand high temperatures.

Before painting, the metal surface should be primed. For this purpose, GF-021 or similar ones are most often used. Its color is gray and red-brown. To reduce the amount of paint used, a more suitable primer is selected. It is applied to a dry, clean surface with a brush, roller or using a spray gun in 1-2 layers.
After the primer has dried, begin painting. To prevent the primer from showing through, the paint will have to be applied in two layers.

Paint "Special Forces"

A clear minus of this product- high price. In all other respects, it is ideal for working with metal surfaces. This is a three-component paint. It contains a rust converter, a primer and the enamel itself.
When working with Spetsnaz, there is no need to apply primer or heavily clean the supports. However, although it is written that it is applied to rust, it is better to remove it. Degreased with either white spirit or solvent 647.
Paint is applied to the cleaned pipe with a brush. After the first layer, there may be unpainted areas, but after applying the second, there will be no such areas. For exterior use three coats are required. “Spetsnaz” dries quickly, therefore, being in an open jar for a long time, it begins to thicken. It is diluted to the desired consistency with the same white spirit.
The enamel is packaged in 900 g jars and comes in ten colors. After drying it takes on a matte finish.
Now there are many names of three-in-one paints: “Rzhavostop”, “Nerzhamet”, “Hammerite” and others. What they all have in common is application to a rusty surface. Although, to clear your conscience, it is better to clean up. And the price range is not cheap.
Although these types have their own advantages, many prefer a primer with or without subsequent painting.
For painting pipes, they also use aluminum silver powder, which is dissolved in varnish for exterior use.

General rules for painting work

In order to successfully complete the planned work, you should adhere to certain rules that can protect you from annoying mistakes.

1. Since most of the materials used are flammable, work should not be carried out near open flames.
2. For painting, you should choose a dry, warm day, since the quality of the layer deteriorates in strong sun.
3. If you have any doubts when purchasing, ask for a product certificate.
4. Use covered clothing and gloves to protect your body from paint.
5. Keep paints and varnishes and solvents should be kept away from direct sunlight and sources of fire.

By fulfilling these simple requirements, the fence will serve for a long time and will not require frequent repairs.

Corrosion is the scourge of all metal structures, and leaking pipes are every homeowner’s nightmare. The appearance of rust is inevitable, like the change of seasons, it is caused by physical and chemical environmental factors. But it is possible to slow down the development of corrosion and reduce its destructive impact.

Metal and plastic: pros and cons

Conventional wisdom in the repair industry is that there is only one radical way combat corrosion - replacing all pipes with plastic ones. But metal pipes don’t give up so easily, because it’s not always possible to make major renovation throughout the apartment. In addition, steel and cast iron pipes much stronger and more reliable than plastic and metal-plastic ones. They are more resistant to high blood pressure and temperature (especially to their differences), have a low coefficient of thermal expansion (do not deform) and high thermal conductivity.

Plastic is theoretically very durable, but this has not yet been tested by time. The safety of this material during long-term use has not been sufficiently studied, but it is already known that it is afraid of chlorinated water. So metal pipes still have a place in our homes, which means that the problem of protecting them from corrosion is still relevant.

There is aggression all around!

How to deal with rust at home? Most affordable way- applying a product to the metal that forms a protective film on its surface: paint, varnish, enamel. Paint and varnish coatings have low vapor and gas permeability and high water-repellent properties. Thus, they do not allow moisture, oxygen and other aggressive substances, which cause corrosion, to reach the metal surface. Paintwork materials are relatively inexpensive and can be easily applied with a regular brush or spray. They save protective properties for several years. Their important quality- resistance to high temperatures, the main disadvantage is sensitivity to mechanical damage and temperature changes, due to which small cracks form on the surface, allowing moisture and air access to the metal. Therefore, staining should be done regularly.

Main quality!

A barrier in the form of paintwork materials does not stop corrosion completely, but only slows it down. Therefore, the quality of the coating comes to the fore - high strength of adhesion of the composition to the base (adhesion), uniform application, absence of porosity and air bubbles. And the quality of the coating is directly related to how the base is prepared. Old, flaking paint must be carefully removed. If the pipe is rusty, then you need to clean off the loose layers, and then use a special rust converter (150-200 rubles / kg). These products are based on acid (usually phosphoric acid). It chemically interacts with rust and turns it into iron salts - a neutral substance that forms a uniform and durable additional protective film.

Next, apply an anti-corrosion primer and only then apply a paint compatible with the primer. The thicker the layer of the latter, the worse the adhesion to the base. Therefore, the main rule is that several are better thin layers coatings than one thick.

The range of anti-corrosion coatings is quite extensive. The simplest ones are GF-021 primer (the cost of this product from the Khimservice company is 50 rubles/kg) and PF-115 enamel (for example, the price for this material from the RegionSnab company is 48 rubles/kg). More expensive, but also effective - polyurethane, alkyd, epoxy coatings, which not only protect the metal well, but also have excellent decorative properties(in particular, enamel “liquid plastic”). It’s good if the paint contains corrosion inhibitors - substances that slow down oxidation. The most convenient to use products are those that are combined under the name “rust paint 3 in 1” (about 200 rubles/kg) - they simultaneously contain a rust converter, an anti-corrosion primer and wear-resistant enamel.

What's underground?

Pipes running underground are especially susceptible to corrosion. suburban area There is no way to do without them. A different corrosion mechanism occurs in the soil than in the atmosphere. The main cause of soil corrosion is electrochemical factors: a metal pipe in the ground becomes an electrode, and wet soil becomes an electrolyte.

Paintwork materials are not suitable for isolating a pipeline from this aggressive environment, since the protective layer is mechanically damaged upon contact with the ground. Much more practical are elastic coatings based on coal tar (bitumen) with various additives, mineral or polymer, that increase its strength. This mixture is called bitumen mastic(from 25 rub./kg). Another option is to wrap the pipes with any insulating material, for example, waterproofing (from 40 rubles / sq. m), which is asbestos paper coated with bitumen with the addition of cellulose.

What's new?

A relatively new effective and inexpensive method of protection against soil corrosion is the use of geotextiles (from 20 rubles/sq. m). This non-woven polymer fabric has excellent water and breathability, is durable, wear-resistant and can withstand high mechanical loads and impacts. aggressive environments. Geotextiles create reliable separation layer between the pipe and the ground. The best effect will be achieved by wrapping the pipe, lining the trench and providing good drainage at the same time. In this case, the water entering the ground is not retained, which means it does not have time to affect the protective coating of the pipe. Synthetics practically do not decompose in the soil, which allows drainage based on them to function for a long time. Working with geotextiles is simple and does not require special qualifications.

A truly unique method of protection is cold galvanizing. Metal-polymer compositions (200-350 rubles/kg) have a protective effect that is comparable to galvanizing performed traditional way- hot or galvanic. Such compositions provide protection in water, soil, and atmosphere for many years; they are used both to obtain independent protective coatings and as primers before applying paintwork materials. The cold galvanizing system contains a binder - polystyrene, epoxy, alkyd and other bases and zinc powder (“zinc dust”), in which approximately 95% of metallic zinc is present with a particle size of less than 10 microns. Apply the composition like regular paint - with a brush or roller. After drying, a polymer-zinc film is formed on the surface, combining all the advantages of polymer and zinc coatings: the first forms a mechanical barrier protection, and the second - electrochemical. In addition, this coating is quite elastic and does not give microcracks, and it is also easy to repair.

Proper anti-corrosion protection will help preserve original appearance various designs and metal pipes. Subject to the selection of quality materials, correct application, careful preparation surface, it will save you from unnecessary costs, save time and effort.